1. Field of the Invention
This invention relates to positioning a moving web and more particularly to positioning the moving web to be in alignment with a predetermined center line of a moving web system.
2. Description of the Prior Art
In web processing systems, it is necessary that certain operations be performed on a continuously traveling web of a thin material such as magnetic tape, film, paper, sheet metal, carpeting, or the like. In most such processing it is necessary that the traveling web be maintained in proper alignment with the machine that operates on the web.
U.S. Pat. No. 3,693,855, entitled, "Web Guide Apparatus," issued Sept. 26, 1972, to William A. Bonner describes an apparatus employing a pneumatic type sensor for determining and correcting the position of a moving web. Still further, U.S. Pat. No. 3,973,446 entitled, "Web Aligner," issued Aug. 10, 1976, to Michael Vasilantone, describes a device employing a mechanical sensor for sensing and maintaining a predetermined alignment of the moving web.
Aligning the elevation axis of a moving web may be a problem particularly manifested at the input area to web processing systems. The web, such as magnetic tape, being fed into the system from the storage reel mounted in the vertical position may have an elevation center line that intolerably changes. The center line changes because the tape stored on the storage reel may loosen and slip in shipment or because vibration in the environment in which the tape is stored causes the relative position of some windings segments or turns of tape to be at a relative height that is lower than the center line of the reel while other segments or turns may be at a height that is higher than the center line of the reel.